The present invention relates to microelectronic packaging and microelectronic assemblies.
There is a need in advanced microelectronics for different types of circuitry to be incorporated into a single microelectronic package or microelectronic assembly including a plurality of circuit panels. For example, it would be desirable to incorporate analog, digital and radio frequency amplification and modulation/demodulation circuitry into a single microelectronic package or assembly. Often, the microelectronic package or assembly has an additional requirement to be compact, provide electromagnetic shielding, and be capable of dissipating excess heat, without requiring additional power-consuming components such as fans and refrigeration equipment. A stacked arrangement is desirable for compactness, provided that adequate shielding and heat dissipation are achieved.
The requirements of such packaging pose special challenges. Typically, digital, radio frequency and analog (baseband) circuitry are implemented on different chips. The packaging must route signals, power and ground to and from each of the chips. Radio frequency (“RF”) chips have high power consumption and high need for shielding. RF chips also need close proximity to ground and power connections. For these reasons, they are desirably disposed at a lowest level of a stacked package. Digital circuitry, which typically has lower power consumption and less need for shielding and proximity to ground and power, usually tolerates placement on a higher level of a stacked package. Analog circuitry generally has a medium need for shielding and proximity to ground and power. Therefore, analog chips must be placed closer to the lowest level of packaging than the digital circuitry.
Thus, the digital circuitry is desirably placed at the top level of a stacked assembly. Because of this, the package is required to route a significant number of digital signal lines from the top level of the package to lower levels on which an RF circuitry chip (hereinafter, “RF chip”) and an analog chip are disposed. At the same time, the package may require the RF signal lines going to and from the RF chip to have well-controlled impedance, and may also require analog signal lines going to and from the analog chip to be shielded differential signal lines.
Multi-layer substrates exist which are capable of implementing the different types of signal lines that are required for carrying digital, analog, and RF signals. However, heretofore, a suitable, cost-effective approach has not been available for interconnecting single conductive layer or multi-layer substrates in a stacked arrangement which satisfies requirements for cost, shielding, controlled impedance signal lines, ground, and/or heat dissipation and for controlling stress due to differential thermal expansion within the package. Moreover, the performance requirements of RF circuitry continue to increase. Required RF signal bandwidth within the package can be 5 to 10 GHz at present, and may increase further in the future.